Radiation induced changes in the blood capillaries of rat duodenal villi: a corrosion cast, light and transmission electron microscopical study.

Disturbances of gastrointestinal function are an important limiting factor in radiotherapy of the abdominal and pelvic regions. The pathogenesis of radiation induced intestinal dysfunction is not completely understood, although the intestinal mucosa has been shown to respond to irradiation by a progressive reduction in villous size. Since blood vessels in other organs have been implicated in the initiation of post-irradiation changes, the present study examines the response of villous blood vessels to an X-ray dose of 10 Gy after 3 days. Vascular corrosion casts and light and transmission electron microscopy (TEM) were used to study the post-irradiation vascular response. In control and sham-irradiated animals, the villous plexus was fountain-like: an arteriole entered the villous base and divided apically into two terminal branches. Villous capillaries apparently derived from the terminal branches, and united to form venules. In capillary loops the vertical inter-capillary distance was greater than the horizontal inter-capillary distance. After irradiation, the vessels became tortuous and the plexus was compressed apico-basally, shown by a decrease in the vertical inter-capillary distance. The capillary luminal diameter, as measured on resin semi-thin sections, was significantly increased. TEM showed that the endothelium was irregular and there was evidence of plasma leakage. These results suggest that villous damage seen after irradiation can include changes in the villous vasculature.